Nanostructured carbon emerged as one of the most promising nano materials of the last decades. Ranging from graphene sheets to fullerenes, nanotubes (CNTs) and diamond like coatings, various types of carbon structures have been developed, each with their own fascinating properties. Besides these well known allotropes, various other interesting types of carbon materials exist that are typically fabricated by pyrolysis of an organic polymer.
Amorphous carbon may be particularly interesting in applications requiring a wide electrochemical stability window, excellent bio-compatibility, and good thermal conductivity.
For these reasons, as well as its cost-effective fabrication, G. Whitesides, M. Madou and others [Schueller, O. J. A., Brittain, S. T. & Whitesides, G. M., Sensors and Actuators a-Physical 72, 125-139 (1999)] have pioneered the application of pyrolysed carbon in microsystems including heat exchangers, chemical probes, lab on a chip systems, biosensors, fuel cells, and it has been implanted over a million times in heart valves and orthopedic joints. Madou et al have studied the application of pyrolysed carbon in microsystems including lab on a chip systems with the integration of 3D carbon-electrode dielectrophoresis [Martinez-Duarte, R., Gorkin, R. A., Abi-Samra, K. & Madou, M. J. Lab on a Chip 10, 1030-1043].
Few methods are developed for the fabrication of amorphous carbon nanowires (CNWs), the most common probably being pyrolysis of electrospun polymers [Sharma, C. S., Sharma, A. & Madou, M., Langmuir 26, 2218-2222]. While this process is interesting for fabricating mats of randomly oriented nanowires, it does not facilitate the fabrication of high aspect ratio structures obtaining anisotropic properties. Further most of the existing fabrication methods for pyrolysed nanowires are not compatible with standard microfabrication techniques.
U.S. Pat. No. 7,534,470 discloses a method for nanotexturizing amorphous carbon using plasma treatment. While this process enables nanoscale roughening the surface, it does not permit the fabrication of nanowires (i.e. nanoscale solid rods made out of amorphous carbon). U.S. Pat. No. 7,534,470 also discloses making carbon nanotubes (i.e. nanoscale hollow tubes made out of SP2 hybridized carbon) on top of pyrolysed structures. This process enables to fabricate hierarchical carbon nanostructures, however this process involves extra fabrication steps, such as the deposition of a catalyst layer for the nanotube growth. This process leads to the formation of carbon nanotubes (a SP2 hybridized carbon lattice) and does not permit the formation of amorphous nanowires. Carbon nanotubes have different morphology, reactivity and functionality than amorphous nanowires.